1. Field of the Invention
This invention relates to novel additives for two component epoxy resin compositions. The invention also extends to a method of filling cracks or joints in concrete with the two component epoxy resin.
2. Description of Related Art
Epoxy resin compositions are well known. They contain the reactive oxirane ring structure: ##STR1## commonly called epoxy. Liquid epoxy resins are commonly converted, through reaction at the reactive epoxy sites into tough, insoluble and infusible solids having wide applications. The liquid epoxy resin is typically provided as part of a two component system, component A containing the liquid epoxy resin, hereinafter termed the resin component, and component B containing the liquid hardener or curing agent, hereinafter termed the hardener component. When mixed together, these components form a pasty resin composition which cures to a flexible or inflexible solid, depending on the particular resin, curing agent and additives employed.
Of the known liquid epoxy resins the most common include those prepared by the condensation of a lower alkylidene-diphenol such as bisphenol A, with an epihalohydrin such as epichlorohydrin in conjunction with sodium hydroxide to form a his (epoxyloweralkoxyphenol) lower alkane or derivative thereof. Lower as used herein throughout the disclosure and claims with alkoxy or alkane or alkylidene refers to C.sub.1-4 units. The most common epoxy resin useful in this invention is that formed from bisphenol A and epichlorohydrin to form 2, 2 -bis [4-(2'3'epoxypropoxy) phenyl] propane, also termed a diglycidyl ether of hisphenol A, which has a typical molecular weight of about 400 daltons. Higher molecular weight homologs of these resins which introduce further reactive sites with additional hydroxyl groups are well known.
Epoxy resins of the type just discussed with molecular weights of about 1000 daltons or greater generally have high viscosities and high solids contents, both of which can limit applications for their use. Use of such resins as sealants is limited because of high viscosities. The term sealant as used herein refers to a resin with utility to fill cracks or joints in a cementitious substrate.
Additives have heretofor been suggested for inclusion in the manufacture of epoxy resins in order to lower the resin viscosity. U.S. Pat. No. 2,901,462 issued Aug. 25, 1959 to Anderson et al, and U.S. Pat. No. 3,145,191 issued Aug. 18, 1964 to Perfetti are exemplary. However, such additives are incorporated during the condensation reaction complicating the manufacture of the epoxy resin itself. It is also known to add solvents such as methyl ethyl ketone or xylene to an epoxy resin to lower the resin viscosity. While the inclusion of the solvent might improve penetration of the resin through the lowered viscosity, the cured resin composition includes voids due to evaporation of the solvent. In fact, none of the above solutions, to the inventors knowledge, provides an epoxy resin composition which can penetrate into cracks or joints in a substrate such as concrete, particularly when the cracks are very fine and deep, while also being able to adhere and cure below the surface and within these deep cracks.
There is a particular need for a crack sealant having good penetration and adherence qualities for concrete substrates. In past years, corrosion to the steel reinforcements in concrete from salt applied to melt winter ice has become a major problem. A sealant for concrete which will penetrate into joints and cracks to limit or prevent such corrosion is desired.